1. Field of the Invention
The present invention relates to a method of and an apparatus for production management for manufacturing products from semi-products and parts.
2. Description of the Related Art
on a product manufacturing or assembling line, parts are supplied to semi-products on the product manufacturing or assembling line to complete desired products. If the number of semi-products varies due to defective components thereof or a change in the production plan, then supplied parts become excessive or insufficient in number. If supplied parts become insufficient in number and a delay occurs in supplementing parts, then the efficiency with which final products are manufactured is lowered. If supplied parts become excessive in number, then it is necessary to retrieve those excessive parts and store them in a warehouse when the type of final products is to change.
Various processes have heretofore been proposed for the purpose of supplying parts efficiently to production lines. For example, an MRP (Material Requirement Planning) process employs a computer for establishing a production plan beforehand, and supplies the number of parts required to produce a predetermined number of products at times when those products are produced. Another process is known as a parts-on-demand process which supplies parts depending on how the production on a production line progresses, so that a constant number of parts are kept on the production line at all times.
Japanese laid-open patent publication No. 4-125205 discloses an automatic warehouse control system which determines the number of parts to be delivered from a warehouse based on data of parts delivered at a given time from the warehouse according to a production plan and the actual number of parts delivered from the warehouse as entered from a terminal, so that parts can stably be supplied even when the production of parts is changed or modified from the production plan. Since the disclosed automatic warehouse control system requires the operator to enter the actual number of parts delivered from the warehouse through the terminal, however, the entered data are not highly reliable, and it is not possible to compare, on a real-time basis, the actual number of parts delivered from the warehouse and the number of parts delivered according to the production plan. Consequently, the automatic warehouse control system is unable to manage the delivery of parts so as not to cause an excess or shortage of parts when the operation of a production line is to be finished.
A parts delivery system disclosed in Japanese laid-open patent publication No. 2-131829 operates to supply parts in synchronism with an assembly line even when a production plan changes or a disagreement occurs between a production plan and an actual production achievement. Specifically, the disclosed parts delivery system reads assembly progress information with respect to products being assembled from bar code data, compares the read assembly progress information with progress data according to a production plan, calculates the type, number, and delivery timing of necessary parts, and instructs a warehouse to deliver the parts and also instructs a conveyor system to convey the parts. The parts delivery system is capable of supplying parts in synchronism with the assembly line to a certain extent. However, because parts are supplied prior to their being assembled on the assembly line, if the number of products that are actually produced varies due to defective products or a failure of the assembly line after the parts are supplied, then the parts are supplied out of synchronism with the assembly line, resulting in an excess or shortage of parts. Furthermore, the parts delivery system requires complex data processing by a computer, such as processing of bar code data and data comparison. As a consequence, the parts delivery system is too expensive and not practical for the application to a small-scale production line for assembling one part on one semi-product, for example.